Why do I get a dark band when using flash above my camera’s sync speed?
Asked 6/4/2016
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2 answers
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I’m using a Canon T6i with a Neewer TT560 Speedlite. At 1/200s the whole frame is exposed, but at faster shutter speeds I get part of the image dark: around 1/400s about 90% is visible, 1/640s about 50%, and 1/1000s only a small portion is lit.
I also tried to change flash settings in the camera menu, but it says the flash is incompatible or turned off.
Why does this happen, and is there any way to use faster shutter speeds with this flash without getting a partially dark frame?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
10y ago
2 Answers
2
At high shutter speeds, the closing shutter curtain chases the opening curtain across the frame, so the shutter is never 100% open. The flash has a very short duration and this means that while the flash is lit only part of the frame is visible through the shutter.
The exact shutter speed that you'll start to see this issue, depends on the model of camera - but it's often around 1/200s (which matches your observations)
If your flash has a "High speed Sync" mode, then you can try using that - this will lengthen the duration of the flash to be lit for the entire shutter duration. This will allow you to use a higher shutter speed, but the exact upper limit will depend on how good the timing of the flash burst is - this depends a lot on the model of flash you're using.
Another relevant question How does high speed sync mode work?
Originally by user46386. Source · Licensed CC BY-SA 4.0
user46386
10y ago
0
Generated from our catalog & community — verify before relying on it.
This is normal flash sync behavior, not a timing fault.
Your T6i has a focal-plane shutter. At or below its flash sync speed (about 1/200s), the whole sensor is uncovered at once, so a single flash burst lights the full frame. Above that speed, the shutter works like a moving slit, so when the flash fires only part of the sensor is exposed—causing the dark band.
The TT560 appears to be a basic manual flash, and the camera message suggests it doesn’t support Canon’s menu-based flash control or high-speed sync (HSS). Without HSS, you generally must stay at or below the camera’s sync speed to avoid partial exposure.
What to do:
- Use 1/200s or slower with flash.
- Control exposure with aperture, ISO, flash power, and flash-to-subject distance.
- If you need faster shutter speeds with flash, use a flash that supports high-speed sync and is compatible with your camera.
So the fix is usually not better timing—it’s using the proper sync speed, or using an HSS-capable flash.
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